Stroke is the third most common cause of death, the most important cause of severe disability, and the most common life threatening neurological condition in the United States. Although much of our national heath care efforts have been directed at treatment of first and recurrent strokes to reduce case fatality and increase independence of survivors, there is compelling evidence that more substantial benefit for society can be realized by identifying and treating patients at high risk for stroke and that even greater benefits may be realized by reducing the average level of causative risk factors in the population. Either of these approaches rely heavily upon sound population-based epidemiological data over time which are needed to define the magnitude of the problem (incidence and prevalence), the specific nature of the problem (subtypes of stroke), and magnitude and nature of causative risk factors and their level of importance. The Rochester Epidemiology Project and Mayo Stroke Center offer the only long-term trend information on stroke in the world and the only resource for incidence, prevalence, and risk factor data in the United States that is based on the total population in a community. The long-term goal of this center is to utilize the unique Rochester resource to provide information that will lead to stroke prevention in the population. The program is divided into five major parts: (1) defining the incidence and prevalence of stroke and stroke subtypes through 1999 and establishing time trends over 55 years with an ongoing database (Brown), (2) assessing the prevalence of clinically apparent and certain "hidden" risk factors in the Rochester population and their impact on cerebrovascular and cardiovascular morbidity and mortality via a prospective community-based survey (Meissner), (3) estimating the independent risk of stroke, stroke subtypes, and TIA for known or suspected stroke risk factors, to estimate population attributable risk for each risk factor over time and to estimate the expected benefits from treatment of certain risk factors in the population by means of a case- control study and ongoing database (Wiebers), and (4) determining the role and relative impact in the population of patent foramen ovale - a prevalent putative cardiac risk factor for producing stroke (Petty). In addition, a fifth component to this program project will involve the application of Rochester, Minnesota stroke population data and methodology to other defined populations which are culturally diverse and/or environmentally distinct.